A new state report says restoring the Hetch Hetchy Valley in Yosemite National Park would be feasible but costly.

Back in the early 1900s, Congress let the City of San Francisco flood the Hetch Hetchy Valley for drinking water. But environmentalists say the reservoir is not essential to providing water to the city anymore and should be turned into a valley again.

In a long-awaited study released yesterday, the state Department of Water Resources says it would be possible to tear down the O’Shaughnessy Dam and drain the Hetch Hetchy Reservoir. Gary Bardini lead the study.

"From a technical perspective, in the body of work here, we don’t see anything that says it’s infeasible."

He says it’s doable but expensive – between $3 billion and $10 billion. But Governor Schwarzenegger stresses the discussion is still very preliminary.

"So it’s really still at an exploration kind of stage. It’s like looking into it and seeing what solution we can come up with. But it would take a while."

The state report doesn’t make any recommendations about next steps but says any further investigation must include input from the federal government which oversees Yosemite.